Research overview

(1) DFT calculations.

DFT is a powerful computational ab initio method to investigate the electronic structure, mostly the ground state, but recently also excitation spectra (phonons), of many particle systems in physics and chemistry. DFT is very effective in providing reliable results in many cases, especially materials that are not strongly correlated. Recently, an advanced DFT approach (LDA/GGA+U) was developed that can handle even strongly correlated systems. Our methodology combines DFT calculations and the effective tight-binding modelling.

(2) Shape wave functions.

Only a finite number of antisymmetric functions, called shapes, is sufficient to generate all wave functions with a given number of fermions. Shapes are superpositions of Slater determinants with roughly equal amplitudes. They cannot be considered as small perturbations of any one Slater determinant, such as the ground-state one. The superpositions obtained are beyond trial-and-error, or any direct insight, so that the algorithm which constructs shapes analytically has characteristics of artificial intelligence. Unlike Slater determinants, shapes provide a highly structured view of many-body Hilbert space. A significant part of the project is to bring shapes to the level of a practical methodology.

(3) Synthesis and characterization of functional materials.

The synthesis effort serves as transfer of knowledge in synthesis of single crystals. This aspect of the project is of strategic importance for the capabilities of the Physics Department in Zagreb and Croatia in general. We consider vigilant characterization of samples to be an essential step for the understanding of intrinsic material properties, inseparable from synthesis itself. Such an approach proved extremely rewarding in the past, to cite single crystals of Hg1201 as an outstanding example.

(4) Development and application of experimental capabilities.

Once the composition of a compound is established, pressure is a major probe for the manipulation of orbital content of active electrons, which is also the principal output of theoretical calculations. Thermoelectric properties of anatase under uniaxial pressurel enable us to assess the stability of electronic phases on change of symmetry of the crystal structure. Application of uniaxial stress lifts the tetragonal symmetry of the crystal lattice in high-Tc superconductors, shedding light on underlying mechanisms driving superconductivity in those materials. We are also installing a mobile pulsed-laser-deposition (PLD) apparatus to the Physics Department in Zagreb for an alternative view on materials studied on the project.